Zero-bias conductance peak in Dirac semimetal-superconductor devices
Zero-bias conductance peak in Dirac semimetal-superconductor devices
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DOI：
10.1103/physrevresearch.2.032002
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发表时间：
2020-07-01
影响因子：
4.2
通讯作者：
Pan, W.
中科院分区：
文献类型：
--
作者：
Yu, W.;Haenel, Rafael;Pan, W.
马约拉纳零模式（Majorana zero mode, MZMs）是实现拓扑量子计算机的基本构建模块，可以出现在超导体和拓扑材料之间的界面上。在微分电导测量中观察到一个大的、量子化的零偏电导峰（ZBCP）是被广泛用于证实MZMs存在的实验特征之一。在这篇论文中，我们报道了在正常金属（钛/金Ti/Au）-狄拉克半金属（砷化镉Cd3As2）-常规超导体（铝Al）的结结构中观察到如此大的ZBCP，其值接近正常状态电导的四倍。我们的详细分析表明，这种大的ZBCP很可能不是由mzms引起的。相反，我们将ZBCP归因于两个相距遥远的超导Al电极之间存在的超电流，由于超电流相的电路和热波动，该超电流表现为零偏置峰，这是Ivanchenko和Zil'berman在50多年前设想的机制[Ivanchenko和Zilberman， JETP 28, 1272(1969)]。因此，我们的结果要求在将大ZBCP的起源分配给多端半导体或拓扑绝缘体/半金属装置中的mzm时非常谨慎。因此，我们提供了确定何时ZBCP绝对不是由MZM引起的标准。此外，我们提出了几个显著的实验结果，超电流效应发生在异常长的距离和干净完美的安德烈夫反射特征。
Majorana zero modes (MZMs), fundamental building blocks for realizing topological quantum computers, can appear at the interface between a superconductor and a topological material. One of the experimental signatures that has been widely pursued to confirm the existence of MZMs is the observation of a large, quantized zero-bias conductance peak (ZBCP) in the differential conductance measurements. In this Letter, we report observation of such a large ZBCP in junction structures of normal metal (titanium/gold Ti/Au)-Dirac semimetal (cadmium-arsenide Cd3As2)-conventional superconductor (aluminum Al), with a value close to four times that of the normal state conductance. Our detailed analyses suggest that this large ZBCP is most likely not caused byMZMs. We attribute the ZBCP, instead, to the existence of a supercurrent between two far-separated superconducting Al electrodes, which shows up as a zero-bias peak because of the circuitry and thermal fluctuations of the supercurrent phase, a mechanism conceived by Ivanchenko and Zil'berman more than 50 years ago [Ivanchenko and Zilberman, JETP 28, 1272 (1969)]. Our results thus call for extreme caution when assigning the origin of a large ZBCP to MZMs in a multiterminal semiconductor or topological insulator/semimetal setup. We thus provide criteria for identifying when the ZBCP is definitely not caused by an MZM. Furthermore, we present several remarkable experimental results of a supercurrent effect occurring over unusually long distances and clean perfect Andreev reflection features.